Strictly speaking people should be using multiple keys so if a device is lost/stolen, you're not left high and dry. Ideally one per device, especially if they don't support some kind of secure enclave.

I keep one in a yubikey protected by a PIN that sits in a safety deposit box, too. This way if I have my laptop, phone, and day-to-day yubikey is a house that suddenly burns down, I'm still ok.